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Intermediate filaments (IFs) make up the cytoskeleton of most eukaryotic cells. In vertebrates, a number of IF proteins have been identified, showing distributions unique to tissue or cell type. Information on helminth IFs is limited to some nematode species. To observe immunofluorescent localization of IFs in helminth tissues, we selected a murine hybridoma clone producing IgM antibody to multiple types of mammalian IF proteins and examined cross-reactivity to helminth proteins. The selected monoclonal antibody (HUSM-9) cross-reacted well with IFs from nematode species such as Toxocara canis, Dirofilaria immitis, Anisakis simplex, and Trichinella britovi; strong immunofluorescence on cryostat sections was detected in the hypodermis, cords, body muscle, smooth muscle of the uterus, and other epithelial structures. In platyhelminths, i.e., adult Schistosoma mansoni, larval Taenia taeniaeformis, adult Taenia crassiceps, and Echinococcus multilocularis protoscolex, the reactivity was weaker than in nematodes, and localized in the body wall muscle and subtegumental tissue. Western blotting of 8 M urea extracts of parasites with the antibody detected a pair of clear bands in nematodes but not in S. mansoni or the cestodes. These results might be explained by sparse distribution of IFs in platyhelminths, or low affinity of the used antibody to platyhelminth IF proteins, or both.

The immunoglobulin E (IgE) response, a hallmark of helminthic infection, is generally considered a major host defense against schistosomiasis mansoni. In support, it was reported that mice with a null mutation of the Ce gene, which are thus incapable of making IgE, developed Schistosoma mansoni worm burdens 2-fold greater than wild-type mice. However, in another study, reduction of the IgE response in mice to a primary S. mansoni infection by anti-IgE treatment resulted in decreased worm burden and fecundity, suggesting that IgE plays a detrimental, rather than beneficial, role for the host in schistosomiasis. In a third study, S. mansoni worm burden and egg production in normal and in IL-4-deficient mice that produce negligible IgE levels did not differ significantly, and it appeared that IgE did not affect parasite survival or fecundity. In an attempt to resolve these controversies, we examined hepatic worm load and egg production in the liver and small intestine of IgE-deficient (SJA/9) and control IgE-producing (SJL/J) mice, 8 wk after S. mansoni infection. No differences were observed in worm burden, total egg production, and number of eggs produced per female worm in the 2 mouse strains, confirming the data that imply that IgE does not play an essential role in primary S. mansoni infection.

Homologous challenge parasite attrition in gerbils, Meriones unguiculatus, chronically infected with Schistosoma mansoni, was investigated by the recovery technique of retrograde portal perfusion. Whereas the animals vaccinated with gamma- or UV-attenuated cercariae of S. mansoni showed a marginal level of resistance, the chronically infected gerbils exhibited significant parasite attrition against a homologous challenge infection. Our data do not corroborate a previous report suggesting a lack of resistance in gerbils with chronic S. mansoni infection. The gerbil represents an additional experimental host for evaluating acquired resistance to S. mansoni, including that induced by previous exposure to irradiated larvae on chronic infection.

Cystic hydatidosis (CH) caused by Echinococcus granulosus is an important zoonosis worldwide. Several serodiagnostic and ultrasound tests are currently used for screening asymptomatic CH. The sensitivity of the serodiagnostic tests has been demonstrated by several groups to be lower than ultrasonography (US). To explain the mechanism of the difference in sensitivity, a large-scale US survey combined with an IgG4-enzyme-linked immunosorbent assay test was conducted in Uruguay. Our results suggest that certain cyst images, e.g., multivesicular cysts, may be closely associated with a high antibody response regardless of the cyst size, whereas other hydatid lesions, e.g., solid images with/without rolled parasite membranes, have lower antibody responses with a close relationship to cyst size. Seropositivity of subjects who had been treated surgically for removal of hydatid cysts in the last 5 yr was closest to that of actual CH patients, albeit free from CH by US. These findings are important for the proper use of serodiagnostic tests and US for community-based epidemiological studies.

Five confirmed human cases of gnathostomiasis nipponica exhibiting creeping eruption and itching were found sporadically from the autumn of 1991 to the winter of 1992 in the northern region of the mainland of Japan. In all cases, a causative gnathostome with 3 transverse rows of hooklets on the head bulb was detected in biopsied skin. The morphological characteristics agreed with the advanced third-stage larvae of Gnathostoma nipponicum. Within a few weeks before development of symptoms, all patients had histories of eating raw freshwater fishes, kokanee (Salmo nerka nerka), carp (Cyprinus carpio), crucian carp (Carassius gibelio langsdorfi), or common ice-fish (Salangichthys microdon). However, they had never eaten raw loach, which is known as a source of human infections with G. nipponicum.

A rare instance of human infection with an acanthocephalan is reported. A species of Bolbosoma, class Palaeacanthocephala, was found at laparotomy in a 51-yr-old Japanese fisherman who complained of acute abdominal pain. The parasite probably was acquired by eating raw fish (sashimi), perhaps bluefin tuna. Infections of humans with Acanthocephala are rare. Most of the reported infections have been with Moniliformis and Macracanthorhynchus (class Archiacanthocephala). Only a few reports of infection of humans by other classes are avail- able (Golvan, 1969; Schmidt, 1971). This paper reports the finding of an acanthocephalan para- site, Bolbosoma sp., in a Japanese man admitted to a hospital for acute abdominal pain. CASE REPORT

The release of Schistosoma japonicum cercariae from Leytean Oncomelania quadrasi snails was observed under laboratory conditions. Two patterns of emergence were noted. The initial, nonperiodic emergence occurred immediately after submerging the snails in water and was followed by a periodic, diurnal emergence which peaked in the afternoon. The daily cercarial output of the periodic emergence appeared to be affected by exogenous light intensity. Furthermore, there was a cessation or reduction in cercarial output every 3rd or 4th day.